69 1 Research Scholar (e mail: nishanbhullar28@gmail.com), 2 Assistant Vegetable Breeder (e mial: mksidhu@pau.edu), 3 Senior Vegetable Breeder-cum-Head (e mail: ajmerdhatt@pau.edu), Department of Vegetable Science. Indian Journal of Agricultural Sciences 88 (6): 877–83, June 2018/Article https://doi.org/10.56093/ijas.v88i6.80634 Heterosis and combining ability for bushy and butternut traits in pumpkin (Cucurbita moschata) NISHAN SINGH 1 , MOHINDER KAUR SIDHU 2 and AJMER SINGH DHATT 3 Punjab Agricultural University, Ludhiana 141 004 Received: 27 February 2017; Accepted: 17 April 2018 ABSTRACT The improvement of pumpkin(Cucurbita moschata Duch ex Poir.) for intensive cultivation necessitates genetic studies, wherein, heterosis and combing ability were studied in half di-allel fashion involving bushy plants and butternut fruits. The genotypes, P-3621 was best general combiner for short vine, internode, equatorial diameter and high fruit shape index, P-6242 for pulp thickness, P-2211 for number of primary branches, P-10224 for polar diameter as well as vegetative growth and P-1343 for petiole length. However, high specific combining ability (SCA) in P-10224 × P-6242, PS × P-6242, P-41212 × P-2211, PS × P-364, P-41212 × P-6242, P-10224 × P-2211 revealed the occurrence of both additive and non-additive gene effects with the predominance of non-additive effects (σ2SCA/ σ2GCA >1) in the inheritance of bushy and butternut traits, which can be exploited through heterosis breeding and recurrent selection in pumpkin. The hybrids, P-3621 × P-2211, P-6711 × P-2211 and P-6711 × P-6242 had high pulp thickness as well as comparable yield potential with the check hybrids and could be exploited for commercial cultivation. Key words: Bushy vines, Butternut fruit, Combing ability, Heterosis, Pumpkin Pumpkin (Cucurbita moschata Duch ex Poir., 2n=40) is known as Halwa kaddu, Sita Phal, Misti kumra or Misti lau or Misti kadu, in India. Among 27 species of genus Cucurbita, it is acknowledged for long vines and big summer hardy fruits conspicuously with large seed cavity and long storage life (Pandey et al. 2003). The vigorous growth habit, occupying more space, leads to less number of plants per unit area. The second practical problem is large fruit that face problem during marketing as one piece. It makes this nutraceutical rich vegetable an uneconomical and unhygienic. Therefore, to counter these issues, dwarf plants bearing small fruits are required. The butternut group of pumpkin has dwarf vines and thick-fleshed fruits. Bushy nature in pumpkin is controlled by a dominant gene (Li et al. 2007, Wu et al. 2007) and is worth to exploit through heterosis breeding. Therefore, assessment of combining ability (GCA and SCA) is prerequisite, which not only provides certain cross combinations with relatively better performance than expected average, but also unveils the occurrence of additive and non-additive genetic variances. Although, information is available on genetic variability, combining ability and heterosis breeding in pumpkin (Pandey et al. 2003 , 2010), but attempt has not been made to explore bushy nature, butternut shape and smaller sized fruits of pumpkin in the country. Therefore, combining ability and economic heterosis studies involving the bush and butternut type genotypes were planned to understand the genetic behaviour of these traits in pumpkin. MATERIALS AND METHODS The experimental material consisted of nine parents. The passport information of all the parents is given in Table 1. During first season (Feb-June 2015), parental lines were grown in crossing block and all possible crosses were made following di-allel mating design with exclusion of reciprocals [n (n-1/2)], along with selfing of individual parents for their maintenance. Seeds of different crosses were harvested separately and stored for next season planting. In second season (February 2016), all F1 hybrids and their parents were grown in randomized block design with three replications as suggested by Snedecor and Cochran (1967). The bush type parents and their crosses were transplanted at 1.5 × 0.45 m (row × plant) spacing on both sides of the beds, while vine parents and their crosses were raised at 3 × 0.60 m (row × plant) spacing on both side of beds, accommodating 10 plants per replication. The observations such as short vine, number of primary branches, internodal length, leaf length, leaf width, petiole length, polar diameter, equatorial diameter and pulp thickness were recorded on five randomly selected plants. The analysis of variance for randomized block design as well as combining ability was done for all the characters as